Antiarrhythmia drugs Flashcards
Class 1A Na+ channel blockers
- Quinidine, procainamide, disopyramide.
- Increase threshold for AP firing.
- Decrease Vmax (lowers rate of upstroke).
- Increase ERP.
Indirect effects:
- Blocks K+ channels (potential for EADs).
- Vagolytic effect (can increase AV conduction - would need to give Digoxin).
Uses: atrial flutter; a fib; prevent v tach and v fib. Contraindicated in patients with LQTS.
Class 1A (quinidine, procainamide, disopyramide)
Lidocaine
- Class: 1B
- Blocks Na+ channels in a use-dependent manner.
- Increase AP threshold.
- Decreases AP duration and ERP.
Use: V tach; digitalis-induced arrhythmias, safe for patients with LQTS.
Class IB (lidocaine)
Flecainide
- Class: 1C
- Increase AP threshold.
- Reduce Vmax.
Side effects: pro-arrhythmic.
Approved for use in life-threatening situations. Really potent. LQTS3.CPVT.
Class 1C (flecainide)
B-blockers
Class II
Propranolol (long-acting), Esmolol (short-acting).
Slow the rate of diastolic depolarization (prolong PR interval). Do not prolong repolarization (safe for LQTS).
Used for all atrial arrhythmias, v tach and v fib.
Class II (b-blockers)
K+ channel blockers
Amiodarone, Sotalol, Dofetilide
Block K+ channels; prolong AP repolarization. Increased ERP. Reverse use-dependence.
Most common target is IKr (hERG channel).
Class III (K+ channel blockers)
Amiodarone
Class III (K+ channel blocker)
- Blocks both IKr, IKs.
- Modest Na+ channel blocker
- Modest Ca++ channel blocker
- Modest B-blocker
Effective against v tach and v fib. Prophylaxis of a fib or flutter.
Not associated with TdP, but yes with hypothyroidism. *Pulmonary toxicity.
Sotalol
Major action is blocking IKr. Also has B blocking actions.
Most serious SE: TdP.
Effective against V tach, v fib, A tach and A Fib.
Administer with caution in conjuction with drugs that prolong the QT interval.
Renal clearance.
Dofetilide
Blocks IKr.
SEs: triggered arrhythmias, TdP.
Most often used for Afib and atrial flutter.
Drugs that interfere with renal secretion system are contraindicated (increase chance of TdP).
Ca++ channel blockers
Class IV (non-dihydropyridines: benzothiazepines, phenylalkylamines)
Act primarily on SA & AV node to slow the rate of depolarization. Increase nodal cell refractory period; increase threshold for AP firing in nodal cells.
Used primarily for paroxysmal SVT.
SEs: bradycardia, negative inotropic effect, hypotension.
Renal excretion.
Class IV (Ca++ channel blockers)